Need Help - Bad Ha Antia 3nm Filter? Antlia 3nm Narrowband H-alpha · Andrew Topper · ... · 14 · 638 · 7

This topic contains a poll.
Should I return this filter?
No - This is "Normal"
Yes- Return Bad Filter
atopper 0.00
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Recently had first light I purchased new SHO narrow band filters. Got the image below when I did flats on the Ha. Never seen a flat look like this. Should I be worried about a damaged filter or is this "normal"? My old set never looked anything like this... I've seen dust and brighter in the center but never this type of pattern. Let me know if I should return these or this is "OK"?

thanks in advance for your advice. Ha.jpg
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messierman3000 7.22
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how do you take your flats?
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atopper 0.00
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I used Nina flat wizard and Pegasus Astro Flatmaster 150 to take flats.
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akshay87kumar 3.01
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Can you check if there is light leaking in from somewhere? Recently I had similar patterns when taking darks for my calibration frames. The cap was not put tightly on the scope, and light was leaking in through t2 filter. Maybe in your case it is light leaking in from somewhere too (filter wheel?)
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atopper 0.00
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I put the scope in a dark room without windows. The S and O filters are looking "normal" to me, below are the two flats that I got:

Oiii_flat.jpgSflat.jpg
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charles.tremblay.darveau 1.20
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Are these mounted or unmounted?
Edit: If you are using unmounted this could be due to a light leak around the filter. You would need filter masks.
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apennine104 3.61
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Hi,

It looks normal to me, but with a reflection. Are you using an OAG? Not Antlia, but my Chroma's looked similar (photo below). This was due to a reflection in my optical train, I believe the OAG. When I flipped the filters, it fixed the issue. So, you might want to try flipping the suspect filter.

Flat_Reflection.jpg
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aabosarah 9.31
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Can you check if there is light leaking in from somewhere? Recently I had similar patterns when taking darks for my calibration frames. The cap was not put tightly on the scope, and light was leaking in through t2 filter. Maybe in your case it is light leaking in from somewhere too (filter wheel?)

I second this. I have seen something similar with my Oiii 50mm unmounted chroma filter and it went away when I used a filter centering mask from Buckeystargazer. It was leak around the filter.
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coolhandjo 2.39
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Same. Ha Antlia 3nm flat . My images turn out fine. Ha Antlia 3nm.JPG
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Daniel.P 0.00
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Did you mentioned the sizes of your filter and sensor ?
Daniel
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Gondola 8.11
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Are you having a problem with the calibrated light stack using this flat?
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atopper 0.00
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These are unmounted and I do have the filter masks from buckeye. These are 36mm filters. I've reached out to Agena astro for their opinion as well. I will let you know what they advise. I'm hoping it's something silly like I have them facing the wrong direction. I tried to make sure I looked at the reflection in the filters to install correctly. I am using an OAG. I'm still in the middle of processing the images from that target and don't see anything weird after stacking… not sure if stacking is smart enough to not apply flats if there's no data anomaly in the frame?

Long story short I appreciate the help and will update this thread when I get a response from Agena.
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Gondola 8.11
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Actually, if your stacks look fine after stretching, you are chasing a problem that doesn't exist. I have seen this time and time again on these and other forums where people fret because the flats look weird yet the stacks look fine. It's not because the software is rejecting the flats, it just means that the flats are doing what they are supposed to do. Eliminating all the inconsistencies in the system from entrance aperture to sensor. My best advice is, if your stacks look fine, there's really no reason to closely examine your flats.
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CoryAstro 0.00
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I recently watched a video where someone had a similar problem and it turned out to be light leaking from an empty, adjacent slot in their filter wheel.
if you are using a filter wheel, and you have an empty space on either side of the Ha filter, then try moving the Ha filter so it is sandwiched between the other filters. Or fill the empty slots in the filter wheel with some cheap dark filters.
​​​​​….just a thought.
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WhooptieDo 10.40
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Looking at the image you provided, I would put money on a reflection being your culprit.  Buckeye masks are not immune to this either.  I've seen it happen on folks who have them.  I dealt with this when using 36mm filters as well.    I worked with the guys at Agena and their first thought was to flip them as well.  I started doing a little bit of digging, and soon the issue became obvious.  




You can clearly see the reflection on the edge of the filter masks in this photo.    Now in this case, these aren't buckeye masks, but they still reflect a tad in the same way.   If you see this at all, you've likely found the reason.       

Try this:   Shine a flashlight down the end of your OTA so you can see all the way to the sensor.   Look for anything shiny.   That is going to be your problem.    Feel free to post a pic in here if you do.    My solution was using a 'vantablack' paint that I found on amazon and painting each filter mask individually.



The difference is huge, zero chance of light reflecting off the masks.     This solved my issue.

I do have to ask though, what camera are you using because your filter edges really shouldn't be that far from the edge of the frame.  It's almost like you're using full frame with 36mm filters.   I'd hope not, but it 'looks' like it.   Either that or your filter wheel isn't centering properly.
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